1. Field of the Invention
This invention relates to a connector, and in particular to a connector forming pan of an expandable tubing assembly. The invention also relates to a method of connecting lengths of expandable tubing.
2. Description of the Related Art
WO93/25800 describes expandable tubing defining overlapping longitudinal slots. On expansion of the tubing, by pushing or pulling a mandrel through the tubing, the slots expand to form diamond-shaped apertures. The expansion is accommodated by deformation of the fingers of metal between the slots, this deformation taking place predominantly at the slot ends, and also by circumferential extension of the parts of the tubing wall beyond the slot ends. In expandable tubing developed by the applicants radial expansion is achieved with the parts of the tubing wall between and beyond the slot ends experiencing little if any deformation, these parts being known as the tubing xe2x80x9cnodesxe2x80x9d.
Arrangements for connecting lengths of slotted tubing are disclosed in WO96/37687 and WO97/21901, the disclosures of which are incorporated herein by reference. Both of these documents describe arrangements in which the end of one length of tubing defines a male coupling portion which is received within a female coupling portion on the other length of tubing and attached thereto.
In another coupling arrangement, the ends of the tubing lengths are received within an external coupling sleeve. However, it has been found that, following expansion, the sleeve contracts radially by a significant extent; this creates a restriction in the bore defined by the tubing.
According to the present invention there is provided a method of connecting lengths of expandable tubing defining overlapping longitudinal slots, the method comprising: providing a tubular connector defining overlapping 10 longitudinal slots and comprising end portions; providing lengths of expandable tubing defining overlapping longitudinal slots and having end portions defining nodes between and beyond the ends of the slots and connecting the connector end portions to nodes of respective end portions of the tubing lengths.
According to another aspect of the present invention there is provided an expandable tubing assembly comprising: a tubular connector defining overlapping longitudinal slots and comprising end portions; lengths of expandable tubing defining overlapping longitudinal slots and having end portions defining nodes between and beyond the ends of the slots; and the connector end portions being; coupled to the nodes of the respective end portions of the tubing lengths.
The formation of the connections between the connector end portions and the nodes of the tubing end portions provides for a relatively secure connection. Preferably, the connector end portions and the nodes of the tubing end portions are threaded, and the absence of significant deformation at the nodes facilitates maintenance of a secure connection on expansion of the tubing lengths and the connector.
Preferably also, the connector further comprises an intermediate portion selected to be of corresponding configuration to the tubing lengths, such that the expansion characteristics of the connected tubing assembly will be substantially constant over the connection.
Preferably also, each connector end portion defines a slot to receive a corresponding tongue provided on the respective tubing length end portion.
According to a further aspect of the present invention there is provided an expandable tubing assembly comprising: a tubular connector defining overlapping longitudinal slots, the connector comprising end portions and an intermediate portion; and lengths of expandable tubing defining overlapping longitudinal slots and having end portions coupled to the connector end portions, at least the connector intermediate portion being of corresponding configuration to the tubing lengths, such that the expansion characteristics of the intermediate portion and the tubing lengths correspond.
This aspect of the invention provides a connector which expands in a compatible manner to the adjacent tubing and thus facilitates reliable expansion of an expandable tubing string.
According to still further aspect of the present invention there is provided an arrangement for coupling lengths of expandable tubing, the arrangement comprising a sleeve defining overlapping longitudinal slots, first and second tubing lengths defining overlapping longitudinal slots, in use the sleeve and tubing lengths being radially expandable by deformation of fingers of material where adjacent circumferentially spaced slots overlap, and connecting means for connecting the sleeve to the ends of the tubing lengths, the deformable fingers of the sleeve being axially spaced from the endmost deformable fingers of the respective tubing lengths.
In use, on expansion of the tubing lengths and the sleeve, the deformation of the sleeve fingers will take place following the deformation of the endmost fingers of the first tubing length and prior to the deformation of the endmost fingers of the second tubing length. It has been found that, following expansion, there is little or no diametrical shrinkage of the sleeve, and the force necessary to expand the coupled tubing ends is approximately half that required to expand tubing ends coupled with a sleeve in which there is substantial overlap between the sleeve and the tubing ends.
The invention also relates to a method for coupling the ends of first and second lengths of expandable tubing defining overlapping longitudinal slots and deformable fingers of material where adjacent circumferentially spaced slots overlap, the method comprising the steps of: providing a sleeve defining overlapping longitudinal slots and deformable fingers of material where adjacent circumferentially spaced slots overlap; coupling the sleeve to the ends of first and second lengths of expandable tubing such that the fingers of the sleeve are longitudinally spaced from the endmost fingers of the tubing lengths; and forcing an expansion member through the connected tubing lengths to expand the sleeve and tubing lengths.
As used herein, the term slots is intended to encompass slots which extend through the wails of the sleeve and tubing, slots which extend only pan way through the walls and any other appropriate weakening of the walls such as lines of bores or scallops.
Preferably, the connecting means are provided at circumferentially spaced locations at the end of the tubing lengths beyond the endmost tubing fingers, and at the ends of the sleeve beyond the respective endmost tubing fingers. The connecting means may comprise pins, rivets, screws and the like for location in appropriate aligned bores provided in the sleeve and tubing lengths. Single fasteners may be provided beyond each tubing finger, or multiple fasteners may be provided.
Preferably also, the unexpanded sleeve is of larger diameter than the tubing lengths. Most preferably, the sleeve and the tubing length are each of substantially constant diameter along their length.
According to a still further aspect of the present invention there is provided an arrangement for coupling lengths of expandable tubing, the arrangement comprising a longitudinally slotted sleeve, first and second tubing lengths defining overlapping longitudinal slots. In use, the tubing lengths are radially expandable by deformation of fingers of material where adjacent circumferentially spaced slots overlap, and connecting means for connecting the sleeve to the ends of the tubing lengths.
The sleeve may be in the form of longitudinally extending strips of metal. Most preferably, the strips are rectilinear. On expansion, the strips of the sleeve move radially outwardly and separate circumferentially. Initially, that is prior to expansion, the strips may be circumferentially connected, by frangible links 119 such as wire, webs of material or one or more welds, to facilitate sleeve handling.
The invention further relates to a method for coupling the ends of first and second lengths of expandable tubing defining overlapping longitudinal slots and deformable fingers of material where adjacent circumferentially spaced slots overlap, the method comprising the steps of: providing a sleeve comprising longitudinally extending strips of material; coupling the sleeve to the ends of first and second lengths of expandable tubing; and forcing an expansion member through the connected tubing lengths to expand the sleeve and tubing lengths.
Preferably, the connecting means are provided at circumferentially spaced locations at the end of the tubing lengths beyond the endmost tubing fingers, and at the ends of the sleeve. The connecting means may comprise pins, rivets, screws and the like for location in appropriate aligned bores provided in the sleeve and tubing lengths. Single fasteners may be provided beyond each tubing finger; or multiple fasteners may be provided.
Preferably also, the unexpanded sleeve is of larger diameter than the tubing lengths. Most preferably, the sleeve and the tubing length are each of substantially constant diameter along their length.